Summarize the structure and composition of the atmosphere. Atmospheric Basics Learning Target I can: Summarize the structure and composition of the atmosphere.

Atmospheric Composition Atmospheric Basics Atmospheric Composition Air is a mixture of many gases, each with its own unique characteristics. About 99 percent of the atmosphere is composed of nitrogen and oxygen, with the remaining one percent consisting of small amounts of argon, hydrogen, carbon dioxide, water vapor, and other gases.

Atmospheric Basics

Structure of the Atmosphere Atmospheric Basics Structure of the Atmosphere The atmosphere is made up of several different layers. Each layer differs in composition and temperature.

Atmospheric Composition Atmospheric Basics Atmospheric Composition Lower Atmospheric Layers The troposphere, the layer closest to Earth’s surface, contains most of the mass of the atmosphere, including water vapor. Most weather takes place in and most air pollution collects in the troposphere. The troposphere is characterized by a general decrease in temperature from bottom to top. The upper limit of the troposphere, called the tropopause, varies in height.

Atmospheric Composition Atmospheric Basics Atmospheric Composition Lower Atmospheric Layers The stratosphere, which is above the tropopause, is a layer made up primarily of concentrated ozone. The stratosphere is heated because ozone absorbs ultraviolet radiation, and air gradually increases in temperature to the top of the layer, called the stratopause.

Atmospheric Composition Atmospheric Basics Atmospheric Composition Upper Atmospheric Layers The mesosphere is above the stratosphere. Temperature drops in this layer due to lower pressure and thinning air. The thermosphere increases in temperature due to exposure to intense solar radiation.

Atmospheric Composition Atmospheric Basics Atmospheric Composition Upper Atmospheric Layers The ionosphere, which is made up of electrically charged particles and layers of progressively lighter gases, is part of the thermosphere. The exosphere, which is composed of light gases such as helium and hydrogen, is the outermost layer of Earth’s atmosphere. There is no clear boundary between the atmosphere and space.